Isometric tiles do not fit because of transparency at the outside edges

Hi guys.
(I hope I got the right subforum…)

I am using Blender to generate an isometric tileset for a 2D game. My problem is that the tiles eventually do not fit together. The outside edges are not fully opaque so the background shines through.
When I disable Anti-Aliasing it is ok. But then my rendered tile does not look.

Is there a way or technic that I can have Anti-Aliasing enabled for my rendering but have my outside edges always fully opaque?

Here is an example of the problem:
http://fs2.directupload.net/images/150322/en2x929n.png

Any chance you could post a larger render? It is hard to tell what is going on?

Larger? This is everything already :wink:

The tiles are only 64x32 pixels in size. On my image in post #1 you see 4 of these tiles put together.